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wateronline.com ■ Water Online The Magazine assessed due to insufficient scientific information and understanding of the mode of the risk 4 . Potential Risks Of Hydraulic Fracturing To Source Water The risks associated with hydraulic fracturing to source water include: Water scarcity: Despite the consumption of high volumes of water, the total volume consumed is relatively small compared to the existing water resources in Canada 4 . Also, in the U.S., the quantity of water withdrawn for hydraulic fracturing is only about one percent of the total freshwater when compared to usage by thermoelectric-power generation, which consumes approximately 40 percent of the total freshwater withdrawal 6,7 . However, in areas with dry climates like Texas, Colorado, and California, the use of water for hydraulic fracturing could compete with other water needs, leading to local water shortages which subsequently degrade water quality. Stray gas contamination: Stray gas (fugitive hydrocarbon gases) contaminates shallow aquifers, leading to salinization of shallow groundwater from hydraulic fracturing fluids through leaking shale gas 3 . Spills and leaks: Surface leaks and spills of flow-back and produced water through insufficient pit lining, onsite spills, overflow, or breaching of surface pits during shale gas operations mainly occur near drilling locations 3 . They contaminate soil, surface water, and shallow groundwater. Toxic and radioactive accumulation: The disposal of treated flow-back and produced wastewater containing naturally occurring radioactive materials (NORM) may lead to accumulation of radium in stream sediments downstream of the disposal sites 5 . The radiation poses environmental and health risks. Insufficient treatment and unauthorized discharge of untreated water from shale gas operations: This was revealed by joint U.S. Geological Survey (USGS) and U.S. Fish and Wildlife Service (FWS) studies, as in the case of Acorn Fork Creek in southern Kentucky in May and June 2007, which linked the deaths of aquatic species to the disposal of untreated wastewater 10 . It was also observed that effluent discharges from treatment sites in Pavillion, WY were known for their high salinity levels (120,000 mg/L), high toxic metals (strontium and barium) and radioactive elements (radium isotopes), and organic makeup (benzene and toluene) 11 . Figure 1 presents the hydraulic fracturing water cycle and the potential source water issues. Potential Threat To Surface Water Sources Surface water contamination from hydraulic fracturing fluid may occur during treatment, storage, or disposal processes when there are accidental spills, leakages, or leaching into the nearby surface water 1 . Hydraulic fracturing wastewater also poses a threat to surface water because it contains other chemicals (metals, dissolved solids, organics, and nucleotides other than the fracking additives) that could overflow, spill, or leach into the groundwater and contaminate nearby rivers or streams 1 . When they are treated, the total dissolved solids (TDS) remain high, and the remaining salts are used as road salts, which enter surface waters. Potential Threat To Groundwater Sources The anticipated groundwater contamination mechanism is related to flow-back waters and hydraulic fracturing fluids, which could lead to upward leakage of natural gas along well casings or natural fractures that allow entry of gas into fresh water aquifers or into the atmosphere 3 . Further studies are needed to White Paper 10 Figure 1. Water use and potential concerns in hydraulic fracturing operations (adapted from EPA, 2011 2 )